Skin tanning and light therapy system

ABSTRACT

A system and method for at least one of skin tanning and phototherapy are provided. The system includes a chamber adapted for at least one of skin tanning and phototherapy and a nanostructure UV light emitting device.

The present application claims benefit of U.S. Provisional PatentApplication Ser. No. 60/473,237, filed May 24, 2003, U.S. patentapplication Ser. No. 10/714,824 filed Nov. 17, 2003 and U.S. ProvisionalPatent Application Ser. No. 60/552,018, filed Mar. 9, 2004, which areincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention is directed generally to tanning and phototherapysystems and specifically to systems which incorporate nanostructure UVradiation sources.

BACKGROUND OF THE INVENTION

The most common method of skin tanning involves the process of exposingskin to ultra-violet light. Health research has shown that both thecondition of under-exposure to ultra-violet light and the condition ofover-exposure to ultra-violet light causes a variety of health problems.Health research has also shown that specific ranges of wavelengths ofultra-violet light are responsible for producing health benefits.Moderate exposure to specific wavelengths of ultra-violet light producesthe greatest benefits with the least amount of health risk. Certainmethods and devices are useful at controlling the quantity and qualityof ultra-violet light exposure in the effort to produce the greatesthealth benefits with the least amount of health risks. Ultra-violetlight quality depends primarily on the ranges of wavelength ofultra-violet light; where the highest ultra-violet light quality is theultra-violet light that produces the greatest net health benefits.

The sun is a primary source of ultra-violet light for tanning. Thequantity of light exposure to the sun is simple to control. The qualityof ultra-violet light exposure by the sun is not simple to control.Lamps that provide alternative sources of ultra-violet light allow fortanning services that do not rely on the sun. These tanning services areavailable and are administered in a controlled environment such as inpersonal care service salons. The industry providing controlled exposureto artificial ultra-violet light is generally referred to as the“indoor-tanning” industry. Indoor-tanning does not implement systemsthat are directly dependent on the sun as the source of ultra-violetradiation. The quality of the indoor-tanning ultra-violet light hasbecome important in differentiating services available within the sameindoor-tanning salon and between competing tanning salons.

Light with wavelengths in the ultra-violet range is often referred to asUV light or UV. UVA, UVB and UVC describe three separate non-overlappingbut adjacent ranges of light fully encompassing the UV light range. Therange of light referred to as UVA generally has the longest set ofwavelengths within the UV range and includes wavelengths between 290 and400. UVA-1 is between 340 and 400; UVA-2 is between 290 and 340; andUVA-3 is between 290 and 310. The range of light referred to as UVCgenerally has the shortest set of wavelengths within the UV range andincludes wavelengths between 160 and 260. The range of light referred toas UVB includes wavelengths between 260 and 290.

The use of the terms UVA, UVB and UVC allow the various properties of UVlight to be categorized in general ways. UVA has the best capability oftanning skin. UVB does not produce a tan in the third layer of skin. UVClight does not produce a tan but can sterilize some biological agentssuch as certain bacteria. Under certain conditions UVB will tan thesecond layer of skin. The second layer of skin when tanned with UVB hasa shedding period of 5 to 8 days. Skin tanned with UVA only has thethird layer of skin tanned which results in a normal shedding cycle of28 days.

Under normal conditions the outer layer of skin, also known as the firstlayer, is composed of dead cells. Normally, dead cells will not producemelanin upon exposure to moderate amounts of UV. The layer under thefirst layer of skin is referred to as the second layer of skin, and iscomposed of active cells that may be functioning in some biologicalmanner and will produce melanin upon exposure to UVB light. UVB skintanning has, what some tanners consider, an additional negative effect,UVB tanning will thicken the second layer of skin and as a resultincreases the visibility of skin lines and wrinkles. UVB tanning createsa shedding cycle of 5 to 7 days which is undesirable when a UVA tan hasa shedding cycle of 28 days. When UVB is combined with UVA the sheddingcycle of the UVA tanned layer is accelerated since the second layer isshed more quickly and the third layer becomes the second layer as aresult and is shed within another 5 to 7 days.

Under normal conditions the layer of skin that will produce melanin whenexposed to UVA light is referred to as the third layer of skin. Inexceptional conditions such as albinism, the third layer of skin is notcapable of producing melanin. For the purposes of this application,albino skin is considered an exception to the norm and will not bereferred to as a third layer of skin but as an albino third layer ofskin.

It is common knowledge that all wavelengths of UV over long exposureperiods damages the skin in various ways. Therefore, it is desirable tolimit the exposure of UV radiation to skin. Alternatively, some UVexposure is generally considered necessary in order to maintain goodhealth in other bodily functions, such as the generation of vitamin-D.Vitamin-D is useful in the absorption of calcium in the body. Therefore,it has been recommended by various health organizations studying thephenomena that moderate exposure to UV light has a net health benefit,whereas over-exposure or under-exposure of UV results in a net healthdeficit. The art of indoor-tanning to remain useful should provide forever increasing controllability of the application of the light therapy.As a light therapy tanning should be applied with specific goals andprocedures to maximize the benefits of the therapy.

For people desiring a tan, the main benefits of UV exposure is theproduction of tanned skin. Tanners enjoy positive psychological andperceived positive social benefits resulting from having tanned skin. Inorder to limit the total amount of UV radiation tanners are exposed towhile maintaining a tan, it is desirable to reduce as much as possiblethe exposure to UV light outside the UVA wavelength range. UVB and UVCwavelength ranges of radiation are by definition not capable of tanningskin with a 28 day shedding cycle and therefore reasonable effortsshould be made to eliminate UVB and UVC from the source of light tannersare exposed to.

Indoor-tanning methods generate UV light from converting electricalenergy to light within devices such as UV fluorescent bulbs and high andlow pressure mercury vapor bulbs are two specific types of light bulbtechnologies. UV light bulbs currently in use have properties of highvoltage, high temperature, and low electrical energy to UV conversionefficiencies under seventeen percent.

Within the fluorescent light bulb category there are a variety of typesthat differ mainly in the percentage of UV light produced in the UVA,UVB and UVC wavelength ranges. For tanners concerned with overexposureto UV light the more desirable fluorescent bulbs have a higherpercentage of light in the UVA-1 wavelength range. Tanners concernedwith overexposure prefer and tend to pay a premium for tanning servicesthat have the least amount of UVB and UVC.

Depending on weather conditions, typically 88% of the UV radiation fromthe sun is UVA, in this case an artificial source with more than 88% ofthe UV radiation is UVA is considered a safer tanning method thansun-tanning. Common fluorescent tanning bulbs and associated serviceshave UV composed between 92.0% UVA to 97.5% UVA. Currently, highpressure quartz metal-halogenide bulbs have in general 98.5% UVA and areconsidered to be the least harmful artificial tanning bulbs currentlyused in indoor-tanning salons.

BRIEF SUMMARY OF THE INVENTION

A preferred embodiment of the present invention provides a system for atleast one of skin tanning and phototherapy, comprising a chamber adaptedfor at least one of skin tanning and phototherapy, and a nanostructureUV light emitting device.

Another preferred embodiment of the present invention provides a systemfor at least one of skin tanning and phototherapy, comprising a firstmeans for at least one of skin tanning and phototherapy, and ananostructure UV light emitting device.

Another preferred embodiment of the present invention provides a methodfor at least one of skin tanning and phototherapy, comprising providingUVA light from a nanostructure UV light emitting device onto a skin of ahuman subject who is located in a chamber adapted for at least one ofskin tanning and phototherapy in order to at least one of tan the skinand to provide phototherapy for the skin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic side views of systems according toembodiments of the present invention.

FIGS. 2, 3, 4A, 4B, 5 and 6 are cross sectional side views ofnanostructure UV light emitting devices according to embodiments of thepresent invention.

FIG. 7 is a bottom view of a nanostructure UV light emitting deviceaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventor has realized that a system for at least one of skintanning and phototherapy may use a nanostructure UV light emittingdevice. This allows a control of the peak wavelength of the UV light aswell as provides UV light with a narrow wavelength distribution (i.e., anarrow peak width). FIGS. 1A and 1B illustrate the system 1 whichcontains a chamber 3 adapted for at least one of skin tanning andphototherapy and the nanostructure UV light emitting device 5. Thesystem 1 may be used solely for skin tanning or for phototherapy or forboth skin tanning and phototherapy depending on the need of the personbeing subjected to the UV light. FIG. 1A illustrates an indoor tanningor phototherapy system for the prone body position, which is commonlyreferred to as a tanning or a phototherapy bed. FIG. 1B illustrates anindoor tanning or phototherapy system for upright body positions, whichis commonly referred to as a tanning or a phototherapy booth.

The nanostructure UV light emitting device comprises at least one of ananoparticle and a nanowire UV light emitting device. Preferably, the UVlight emitting device emits only UVA light. The term UV light includesradiation having a peak wavelength between 160 and about 400 nm ratherthan visible light having a wavelength between above about 400 and belowabout 700 nm. UVA light has a peak wavelength between about 290 andabout 400 nm. The nanoparticles and nanowires emit light (i.e.,radiation) with a very narrow peak width due to their size rather thandue to their chemical composition. Thus, in contrast to conventionalceramic phosphors which emit light with a broad peak width due to theirchemical composition and activator ion content, nanoparticles andnanowires emit light with varying peak wavelength due to varying theirsize (i.e., diameter or thickness). Furthermore, some materials, such assilicon, which ordinarily do not emit light in bulk form, emit light innanoparticle form due to the nanoparticle size. Thus, the nanoparticleor nanowire size may be selected such that the nanoparticles ornanowires emit only UVA light, but no UVB light. Furthermore,nanoparticle or nanowire size may be selected such that thenanoparticles or nanowires emit only UVA-1, UVA-2 and/or UVA-3 lightdepending on the desired effect, since the peak width of the emitted UVlight is narrow.

Nanoparticles may be any suitable nanoparticles, such as nanocrystals orquantum dots, having a diameter less than 100 nm, such as a diameter of2-20 nm, for example. For example, metal, semiconductor, as well asmetal or semiconductor oxide and/or nitride nanoparticles may be used.Semiconductor nanoparticles include materials from Groups IV (Si, Ge,SiC, SiGe), II-VI (CdS, ZnS, CdSe, ZnSe, ZnTe, CdTe), IV-VI (PbS, PbSe,PbTe) or III-V (GaAs, GaP, GaN, InP, InAs). Ternary and quaternarysemiconductor nanoparticles, such as CdZnS, CdZnSe, CdZnTe, CdZnTeSe,CdZnSSe, GaAlAs, GaAlP, GaAlN, GaInN, GaAlAsP and GaAlInN for example,may also be used. Ceramic or metal oxide nanoparticles may also be used,such as silica, alumina, titania, zirconia, yttria stabilized zirconia,yttria, ceria, spinel (for example, MgO*Al₂O₃) and tantalum pentoxide,as well as other suitable ceramics having a more complex structure, suchas radiation emitting phosphors (for example, YAG:Ce (Y₃Al₅O₁₂:Ce) andvarious halophosphate, phosphate, silicate, aluminate, borate andtungstate phosphors) and scintillators (for example, LSO, BGO, YSO,etc.). Other metal oxide nanoparticles, such as zinc oxide, indium oxideor indium tin oxide or metal nitride nanoparticles, such as aluminumnitride may also be used. Metal nanoparticles may be pure metal or metalalloy nanoparticles, such as Al, Fe, Cu, Ni, Au, Ag, Pt, Pd, Ti, V, Ta,W, Mn, Zn, Mo, Ru, Pb, Zr, etc. and alloys thereof.

Other materials, such as Boron Carbide, Titanium Oxide (TiO), SiliconCarbide (SiC), Antimony (Sb), Arsenic (As), Bismuth (Bi), Cadmium (Cd),Carbon (C), Gallium (Ga), Germanium (Ge), Indium (In), Phosphorus (P),Selenium (Se), Sulfur (S), Tellurium (Te), Calcium (Ca), Chromium (Cr),Cobalt (Co), Magnesium (Mg), Tantalum (Ta), Silicon Arsenide GermaniumTelluride (SiAsGeTe), Vanadium Oxide, Zinc Germanium Phosphide (ZnGeP2),Zinc Germanium Phosphide (ZnGeP), Aluminum Antimonide (AlSb), AluminumArsenide (AlAs), Aluminum Phosphide (AlP), Gallium Selenide (GaSe),Gallium Telluride (GaTe), Indium Antimonide (InSb) and Silicon ArsenideTelluride (SiAsTe) may also be used.

Nanoparticles may be provided in the UV light emitting device 5 in anysuitable form. For example, the nanoparticles may be located as a solidlayer or layers on a UV transparent and UV resistant material substrate.The solid layer may also contain a UV transparent and UV resistantbinder or filler if desired. Alternatively, the nanoparticles may belocated in a suspension. The fluid of the suspension may comprise anysuitable UV transparent fluid. Preferably, the fluid comprises afluorocarbon fluid, such as perfluorocarbon, chlorofluorocarbon orhydrofluorocarbon fluid. For example, the fluid may comprise 1,1,1,2tetrafluoroethane also known as R134A or perfluorocarbon fluids soldunder the PPx series from F2 Chemicals Ltd. in Lea Town, U.K., such asthe PP6 perfluorocarbon fluid. The R134A fluid is provided underelevated pressure to remain in the liquid state at room temperature.Other fluids which are liquid at atmospheric pressure at roomtemperature may also be used. If the nanoparticles are located in asuspension, then the suspension is located in a sealed vessel or tubemade of a UV transparent and UV resistant material. If desired, thedevice 5 may also contain a pump or vibrator which maintains thesuspension under turbulent flow to prevent the nanoparticles fromsettling on the surface of the vessel.

Nanowires may be any suitable nanowires having a thickness (i.e.,diameter) of less than 150 nm, such as a thickness of 70-100 nm, forexample. The nanowires may comprise any suitable material, such as metaloxide material. For example, zinc oxide, indium oxide and indium tinoxide nanowires may be used. Any suitable length of nanowires may beused.

The system 1 further preferably comprises a UV excitation source 7. Thesource 7 is positioned to provide UV excitation radiation of a firstpeak wavelength onto the nanostructure UV light emitting device 5 tocause the nanostructure UV light emitting device to emit UVA lighthaving a second UVA peak wavelength longer than the first peakwavelength. Any suitable UV excitation source may be used.

In one preferred embodiment shown in FIG. 2, the UV excitation source 7comprises a gas vessel comprising a gas which is adapted to emit the UVexcitation radiation in response to a stimulus. For example, the sourcemay be a gas lamp tube filled with a gas such as Ar or Hg which emits UVradiation when a voltage is applied to the electrodes 9 of the gas tube.The UV light emitting device 5 in this embodiment comprises at least onelayer of nanoparticles coated on an inner surface of at least one UVlight transparent wall of the gas vessel or tube 7. In other words, theconventional phosphor in a fluorescent lamp 7 is replaced with orcombined with one or more layers of nanoparticles which emit UVA lightin response to UV excitation radiation emitted by the gas. In this case,rather than using an expensive UV emitting lamp, a cheap germicidal orwhite light emitting lamp may be used instead, but with replacing thewhite light emitting phosphor with UVA light emitting nanoparticles.Preferably plural layers of nanoparticles are coated on the innersurface of the gas tube or vessel 7 to prevent the UVB or UVC radiationemitted by the gas, such as 254 nm UVC radiation, from being incident onthe skin of a person in the tanning or phototherapy chamber 3. The UVexciting radiation from the gas in vessel 7 is incident on thenanoparticles 5, which emit UVA light in response to the incidentradiation. The nanoparticles 5 block the UV excitation radiation, suchas UVC radiation, from exiting the vessel or tube 7.

In another preferred embodiment shown in FIG. 3, the UV excitationsource 7 comprises any suitable UV lamp which optionally contains a UVemitting phosphor 6 on its inner walls. The UV light emitting device 5comprises at least one layer of nanoparticles coated on an outer surfaceof the UV lamp 7. The UV exciting radiation from the lamp from the lamp7 is incident on the nanoparticles 5, which emit UVA light in responseto the incident radiation.

Various other UV excitation sources 7 may be used. For example, the UVexcitation source may comprise a focusing lens which focuses solarradiation onto the UV light emitting device. Furthermore, while anoptical UV excitation source 7 is preferred, in an alternative aspect ofthe invention, an electrical excitation source may be used instead. Inthis case, the nanoparticles or nanowires 5 are located between twoelectrodes. At least one electrode is preferably made of an electricallyconductive and UV transparent material, such as indium oxide, tin oxideor indium tin oxide (ITO). When a voltage is applied between theelectrodes, the voltage causes the nanoparticles or nanowires to emit UVlight.

It should be noted that the nanoparticles or nanowires 5 do not have tobe placed directly on the UV excitation source 7. The nanoparticles ornanowires may be located on a separate substrate, such as a UVtransparent substrate, or in a separate suspension in a vessel, which islocated between the UV excitation radiation source 7 and the portion ofthe chamber 3 which houses the person undergoing tanning orphototherapy.

In a third embodiment shown in FIG. 4A, the UV light emitting device 5comprises a plurality of layers of nanoparticles or nanowires arrangedin a direction extending from the UV excitation radiation source 7 tothe portion of the chamber 3 which houses the person undergoing tanningor phototherapy. The nanoparticles or nanowires in each layer emitradiation having a different peak wavelength from the nanoparticles ornanowires in other layers. Preferably, the peak wavelength of the UVradiation emitted by the nanoparticles or nanowires increases in eachsubsequent layer in the direction from the UV excitation source 7 to theportion of the chamber 3 which houses the person undergoing tanning orphototherapy. In other words, the nanoparticles or nanowires in eachlayer located closer to the person's skin (i.e., further from the UVexcitation source 7) emit radiation of a longer wavelength that those inanother layer located further from the person's skin (i.e., closer tothe UV excitation source 7). This allows the stacked layers ofnanoparticles or nanowires to gradually or stepwise upconvert the UVBand/or UVC radiation emitted by the UV excitation radiation source 7 todesired UVA radiation. There may be two or more layers of nanoparticlesor nanowires.

For example, as shown in FIG. 4A, the UV excitation radiation source 7may emit 254 nm peak UVC radiation. A first layer 11 of firstnanoparticles or nanowires is located proximal to the UV excitationsource 7. The first nanoparticles or nanowires emit UV light of a thirdpeak wavelength, such as 315-340 nm, which is longer than the 254 nmpeak wavelength, when irradiated with the UV excitation radiation fromsource 7. A second layer 13 of second nanoparticles or nanowires islocated distal from the UV excitation source, such that the first layer11 is located between the second layer 13 and the UV excitation source7. The second nanoparticles or nanowires emit UV light of the secondpeak wavelength longer than the third peak wavelength when irradiatedwith the UV light from the nanoparticles or nanowires of the first layer11. For example, the nanoparticles or nanowires of the second layer 13may emit UVA-1 radiation having a peak wavelength of 345-355 nm or395-405 nm when irradiated with UVA-2 or UVA-3 radiation from the firstlayer 11. Additional layers of nanoparticles or nanowires may be locatedbetween layers 11 and 13 to make the radiation wavelength upconversion(i.e., energy down conversion) even more gradual.

Layers 11, 13 may be formed directly on each other with the UVexcitation source 7 acting as a substrate. Alternatively, each layer 11,13 may be spaced apart from the adjacent layer and each layer may beformed on a separate UV transparent substrate, such as glass, plastic orquartz substrate, or in a separate solution holding vessel.

FIG. 4B illustrates an alternative aspect of the third embodiment. Inthis aspect, three layers of nanoparticles or nanowires 11, 12 and 13are arranged in a clam-shell type housing 25 comprising an opaque body.The UV excitation source 7 is located in the interior portion of thehousing 25. A mirror 27 shields the back side of the source 7. The firstlayer 11 of nanoparticles or nanowires is located opposite to the source7 and mirror 27, such that UV excitation radiation from source 7 andmirror 27 is incident on the first layer 11. The second layer 12 ofnanoparticles or nanowires emits UV light having a peak wavelengthbetween those of the first 11 and third 13 layers. The second layer 12is positioned in the housing to receive UV light from the first layer 11and to emit UV light of a longer wavelength onto the third layer 13. Thethird layer 13 is positioned to receive UV light from the second layer12 and to emit UV light of an even longer wavelength out of the housingthrough a lens 29 and through an optional long wavelength filter, whichblocks shorter wavelength UV light from the source 7, first layer 11 andsecond layer 12 from exiting the housing 25. If desired, a lightabsorbing surface may be located behind the layers 11, 12 and 13. Itshould be noted that the term “layer” as used herein includes ananoparticle or nanowire solid layer as well as a nanoparticlesuspension located in a vessel. By using the clam-shell shaped housing25, UV light of one or more desired wavelengths from layers 11, 12and/or 13 exits the housing 25.

In a fourth embodiment of the present invention shown in FIG. 5, anoptical filter 15 is located between the UV excitation source 7 and theUV light emitting device 5. The filter 15 is transparent to the shorterwavelength UV excitation radiation from source 7. However, the filter 15reflects UV light of a longer peak wavelength emitted by the UV lightemitting device 5. The filter 15 may be a holographic filter or anyother suitable filter having the above described property. Thisconfiguration is advantageous when nanoparticles are used as the lightemitting device 5. The nanoparticles emit UV light in all directions.However, the filter 15 reflects UV light emitted toward the source 7back in the direction of the portion of the chamber 3 in which theperson is to be located.

The fifth embodiment is a combination of the third and fourthembodiments. As shown in FIG. 6, the UV light emitting device 5comprises a plurality of layers 11, 13 of nanoparticles or nanowiresarranged in a direction extending from the UV excitation radiationsource 7 to the portion of the chamber 3 which houses the personundergoing tanning or phototherapy. The nanoparticles or nanowires ineach layer 11, 13 emit radiation having a different peak wavelength fromthe nanoparticles or nanowires in other layers. The peak wavelength ofthe UV radiation emitted by the nanoparticles or nanowires increases ineach subsequent layer in the direction from the excitation radiationsource 7 to the portion of the chamber 3 which houses the personundergoing tanning or phototherapy. A filter 17 is located betweenadjacent layers of nanoparticles or nanowires. The filter 17 istransparent to the shorter wavelength UV light from the layer 11proximal to the UV excitation source 7. However, the filter 17 reflectsUV light of a longer peak wavelength emitted by layer 13 distal from theUV excitation source 7. If the device 5 contains more than three layersof nanoparticles or nanowires, then a different filter may be locatedbetween each pairs of layers.

In a sixth embodiment, the nanoparticles or nanowires are arranged inpixels as shown in FIG. 7. The nanoparticles or nanowires in each pixelcan be separately activated by a dedicated UV excitation radiationsource or by dedicated electrodes to selectively tan or treat a desiredportion of skin on the person undergoing tanning or phototherapy. In oneaspect of the sixth embodiment, the UV light emitting device 5 includesa first set of pixels 19 of first nanoparticles or nanowires. The firstnanoparticles or nanowires are adapted to emit UV light having apredetermined first peak wavelength. The device 5 also includes a secondset of pixels 21 of second nanoparticles or nanowires. The secondnanoparticles or nanowires emit UV light of the second peak wavelengthlonger than the first peak wavelength. If desired, additional sets ofpixels may be provided. Pixels of the first set of pixels 19 areinterspersed with pixels of the second set of pixels 21.

All pixels may be turned on at once to provide UV light having aplurality of different peak wavelengths or one set of pixels may beselectively activated while the other sets remain turned off. In thiscase, the peak wavelength of the UV light may be selectively tailoredfor each individual based on the desired darkness of the tan, theindividual's skin color or a selection of a particular wavelengths totreat a particular condition during phototherapy.

In a seventh embodiment, the system 1 contains the UV light emittingdevice 5 with exchangeable nanoparticles or nanowires to vary the peakemission wavelength of the device 5. For example, if the nanoparticlesare located in a suspension in a sealed vessel, then the vessel may beopened and the suspension replaced by another suspension havingnanoparticles which emit light of a different wavelength from thenanoparticles in the original suspension. Preferably, the vesselcomprises non-stick surfaces to prevent nanoparticle adhesion.Alternatively, the entire vessel housing the suspension may be removedfrom the system and replaced with another vessel containing a differentsuspension of different nanoparticles which emit light of a differentpeak wavelength than the nanoparticles of the original suspension. Ifthe nanoparticles or nanowires are coated as a solid layer on asubstrate or substrates, then the substrate or substrate may be easilyremovable from the system to allow the system operator to insert asubstrate or substrates containing nanoparticles or nanowires which emitlight of a desired peak wavelength into the system 1.

A method of operating the system 1 for at least one of skin tanning andphototherapy includes providing UVA light from a nanostructure UV lightemitting device 5 onto a skin of a human subject who is located in achamber 3 adapted for at least one of skin tanning and phototherapy inorder to at least one of tan the skin and to provide phototherapy forthe skin. Phototherapy includes but is not limited to slerodermatherapy, psoriasis therapy, lupus therapy, photopheresia, andphotochemotherapy.

The method also includes providing UV excitation radiation of a firstpeak wavelength from a UV excitation source 7 to the UV light emittingdevice 5. The method also includes emitting the UVA light having asecond UVA peak wavelength longer than the first peak wavelength fromthe UV light emitting device 5 in response to the provided UV excitationradiation.

In an eighth embodiment, blue light having a wavelength of about 400 toabout 415 nm, such as about 405 nm is used instead of UV light. Light ofthis wavelength is sometimes called violet or purple rather than blue.Any suitable blue or violet light emitting device 5 which emits light ofthis wavelength may be used, including a lamp, a light emitting diode,nanoparticle or nanowire containing device 5. The light emitting diode,nanoparticles and nanowires are preferred because they have a narroweremission peak width. For light emitting diodes, blue light emittingdiodes based on GaN, SiC or ZnSe semiconductor materials may be used.Tanning with light in the 400-415 nm wavelength range may provide alonger lasting tan than tanning with UV light. Preferably but notnecessarily, the light emitting device emits light having substantiallyno wavelengths outside the about 400 nm to the about 415 nm range, suchas emitting less than 1% of light having wavelengths outside the about400 nm to the about 415 nm range. The device 5 of this embodiment may beused in combination with the configuration(s) of the other embodimentsdescribed herein.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andmodifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention. Thedrawings and description were chosen in order to explain the principlesof the invention and its practical application. It is intended that thescope of the invention be defined by the claims appended hereto, andtheir equivalents.

1. A system for at least one of skin tanning and phototherapy,comprising: a chamber adapted for at least one of skin tanning andphototherapy; and a nanostructure UV light emitting device; wherein: aUV excitation source is positioned to provide a UV excitation radiationof a first peak wavelength onto the nanostructure UV light emittingdevice to cause the nanostructure UV light emitting device to emit UVAlight having a second UVA peak wavelength longer than the first peakwavelength, wherein the nanostructure UV light emitting device comprisesat least one of a nanoparticle or a nanowire device for emitting onlyUVA light.
 2. The system of claim 1, wherein the system performsskin-tanning.
 3. The system of claim 1, wherein the system performsphototherapy.
 4. The system of claim 1, wherein the system performs bothtanning and phototherapy.
 5. The system of claim 1, wherein the chambercomprises a bed or a booth.
 6. The system of claim 1, wherein the UVlight emitting device comprises nanoparticles having an average diametersmaller than 100 nm or nanowires having an average thickness smallerthan 150 nm.
 7. The system of claim 1, wherein the UV light emittingdevice comprises a UVA-1 light emitting device and the nanoparticlesemit only UVA-1 light due to their size.
 8. The system of claim 1,wherein the UV light emitting device comprises: a first layer of firstnanoparticles or nanowires located proximal to the UV excitation source,wherein the first nanoparticles or nanowires emit UV light of a thirdpeak wavelength longer than the first peak wavelength when irradiatedwith the UV excitation radiation; and a second layer of secondnanoparticles or nanowires located distal from the UV excitation source,such that the first layer is located between the second layer and the UVexcitation source, wherein the second nanoparticles or nanowires emit UVlight of the second peak wavelength longer than the third peakwavelength when irradiated with the UV light from the nanoparticles ornanowires of the first layer.
 9. The system of claim 1, wherein: the UVexcitation source comprises a gas vessel comprising a gas which isadapted to emits the UV excitation radiation in response to a stimulus;and the UV light emitting device comprises at least one layer ofnanoparticles coated on an inner surface of at least one UV lighttransparent wall of the gas vessel.
 10. The system of claim 1, wherein:the UV excitation source comprises a UV lamp; and the UV light emittingdevice comprises at least one layer of nanoparticles coated on an outersurface of the UV lamp.